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A. Giguere, M.-J. Fredette, D. R. Anderson; Reproducibility of Scanning Laser Polarimetry in Glaucoma Patients With a Range of Severity of Disease. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4645. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the intersession reproducibility of scanning laser polarimetry between variable and enhanced corneal compensation (GDx VCC and GDx ECC) in patients with a range of severity of glaucoma.
50 stable glaucoma subjects underwent structural testing with the GDx VCC and GDx ECC on 5 different days in a 8 weeks period. The same GDx unit was used by the same operator for all measurements. Intraclass correlation coefficient (ICC), coefficient of variation (COV), Standard Deviation (SD) and Mean Value (MV) were calculated for TSNIT-Average(Avg), Superior Average, Inferior Average, TSNIT-SD, NFI and Symmetry parameters for both VCC and ECC.
ICCs ranged between 0.85 (symmetry) to 0.97 (TSNIT-Avg) for VCC and between 0.88 (symmetry) to 0.97 (TSNIT-Avg) for ECC. For each parameters tested, ICCs were not significantly different between ECC and VCC (p>0.05). SDs were also not significantly different (TSNIT-Avg SD of 1.5 microns and 1.4 microns for VCC and ECC respectively, p>0.05). MVs were, however, significantly different for TSNIT-Avg and TSNIT-SD. MV of TSNIT-Avg was 44.6 microns with VCC while 40.5 microns with ECC (p<0.0001) and TSNIT-SD were 15.1 and 18.2 microns respectively for VCC and ECC (p<0.0001).
Enhanced corneal compensation provides significantly smaller TSNIT-Avg values compared to variable corneal compensation, which could account for the correction of atypical birefringence patterns sometimes found with the VCC. Both scanning laser polarimetry softwares (GDx VCC and GDx ECC) have good intersession reproducibility. Even though this could suggest that GDx may provide useful information in the follow-up of glaucoma patients, further research are needed to understand the clinical significance on glaucoma progression of changes in scanning laser polarimetry.
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